Frontiers of the Lower Palaeolithic expansion in Europe: Tunel Wielki Cave (Poland)

Peopling of Central Europe by Middle Pleistocene hominids is highly debatable, mainly due to the relatively harsh climatic and environmental conditions that require cultural and anatomical adjustments. At least several archaeological sites certify human occupation in the region dated back to MIS 13-11, but they represent open-air settlements. Based on the new fieldwork conducted in Tunel Wielki Cave, we can date the human occupation traces in the cave to MIS 14-12. Bipolar-on-anvil knapping technique prevails in the lithic assemblage, made exclusively in flint. The obtained results have given ground for studying the frontiers of human oikumene and the required cultural adaptive abilities.


Datings: OSL dating procedure
In the laboratory, a sample was dried. High-resolution gamma spectrometry using a HPGe detector manufactured by Canberra was carried out to determine the content of U, Th and K in the samples. Before measurement, the sample was stored for about 3 weeks to ensure equilibrium between gaseous 222 Rn and 226 Ra in the 238 U decay chain. The measurement lasted for at least 24 hours. The activities of the isotopes present in the sediment were determined using IAEA standards RGU, RGTh, RGK after subtraction of the detector background. Dose rates were calculated using the conversion factors of Guerin et al. 1 . For beta dose rate, the cosmic ray dose-rate to the site was determined as described by Prescott and Stephan 2 . We assumed that the average water content was (18±5)%. For further calculations, a mean a-value of 0.08 for fine-grained quartz 3 was used.
For OSL measurements, fine grains of quartz (4-11 μm) were extracted from the sediment samples. The first step was to obtain the fraction below 45 μm using sieves; next, sediments were treated with 20% hydrochloric acid (HCl) and 20% hydrogen peroxide (H2O2). Finally, the material was etched by concentrated hydrofluorosilicic acid (34%, H2SiF6) for few days; after that, grains were ready for gravitational separation.
All OSL measurements were made using an automated Risø TL/OSL DA-20 reader. The stimulation light source was a blue (470 ± 30 nm) light-emitting diode (LED) array delivering 50 mW/cm2 at the sample 4 . Detection was through 7.5 mm of Hoya U-340 filter. Equivalent doses were determined using the single-aliquot regenerative-dose (SAR) protocol 5

Micromorphological analyses
Layer F was the uppermost loamy layer containing stone artefacts, therefore the analyses focused at answering question about the depositional processes taking place below, above and within layer F. According to Madeyska 1 , Layer F is greyish brown loam with rounded limestone clasts and with cultural relics. A presence of large limestone blocks limits the readability of layer's boundaries. T. Madeyska, on the basis of regional scale litho-stratigraphic correlation, linked this layer with an early part of the Last Glaciation (MIS 5d-5a), a relatively warm and humid period, most likely MIS 5a. She linked other loamy layers (G down to N) with the earlier part of MIS 5. Layer F is the last (the uppermost) unit of this loamy series. Its upper boundary is erosional and covered by loess-like sediment of clearly different lithology.
Layer F, together with lower sedimentary units (layers G down to K), shows distinct inclination (around 30° toward E and 30-40° toward S). Analysis of spatial distribution of the mentioned layers reveals, however, that this inclination has limited range. The cross-section achieved by W. Chmielewski and T. Madeyska 1 documents a U-shaped bending of these layers, which more-or-less reproduces the concave morphology of the bedrock. Such a layout may be interpreted as post-depositional plastic deformation likely related to subsidence, which was possibly caused by compaction of underlying sediments, partial dissolution of bedrock and calcareous components of older sediments, and/or presence of empty spaces somewhere below. It is possible that the cave is connected with another cavity called Rockshelter under Tunel Wielki and a Rockshelter above Niedostępna Cave (Fig.2). This is supported by a vertical chimney of ca. 1 m in diameter situated in the bottom of the cave, which was found in the northern chamber 1 . It was excavated down to 1.6 m without reaching the bedrock. It was filled with mixed loamy and silty sediments (Fig.3).
Layer F exhibits typical micromorphological features of sediments deposited in low-energy environment of a cave floor: massive structure, silty clay grain size composition, and presence of numerous bone and tooth fragments (which correlates with other known sites 2-4 ). Bone and tooth fragments are chaotically oriented and some of them are in sub-vertical position ( Fig.S4: a, b), which likely indicates a re-orientation by some post-depositional agents, such as frost action 5,6 and/or colluvial activity 7,8 . Planar voids are frequent and parallel to each other. Some of them cut through larger grains and aggregates. This suggests that the voids may represent a remnant of ice lenses which are known to produce similar structure 6 , so called lenticular microstructure of sediment, and are common in periglacial environments. In opposition to typical periglacial lenticular structure, here the planar voids are inclined. However, their inclination reproduces the general dip of the strata boundaries. This suggest that the voids could possibly have been originally oriented sub-horizontally and were re-oriented together with the entire sediment packet by the subsidence. The inclined orientation of presumably originally horizontal planar voids suggests that the frost action that produced the voids happened before the subsidence. The survival of voids, stratigraphic unit boundaries and other microfeatures indicates that the re-orientation process involved the whole packet of now-inclined layers, without disturbing their inner structure. Similar inclined planar voids occur also within layer G and weakly developed ones in layer H (Fig.S8: e-h), which indicates that the frost action event affected the entire packet of layers F-G-H. The presence of aggregates or small (c. 1 mm size) diapirs of layer's G just above the layer F/layer G boundary ( Fig.S4: c, d) may also be another effect of frost action. Similar plastic deformations at layer boundaries are known from other cave sites 4 and related to frost action.
Original depositional processes cannot be exactly characterized for layer F, as most of original sedimentary features were disturbed by later frost action and subsidence. However, it is clear that the material of layer F is different from the sediments of underlying layers G and H. This dissimilarity is visible in grain size composition (layers G-H much more clayey), b-fabric (birefringence colors much more intense in layers G-H), color (layer F more greyish and layers G-H more brownish in plane polarized light; layer F also paler and less yellowish in crosspolarized light), and abundance of bone and tooth fragments (much more abundant in layer F) (Fig.S8, Table S9). The material of layer F can be therefore regarded as an effect of new depositional event and supply of fresh clastic material, and not any important re-deposition of older sediments. Bone and tooth fragment are abundant in layer F. These are angular fragments, mostly below 0.5 mm in size, with traces of in situ cracking ( Fig.S8: a, b), which is a phenomenon known from other cave sites and related to frost action 2 . In layer G some bone fragments bear corrosive pits, likely an effect of digesting due to carnivore activity. Such features were not observed in layer F, which may indirectly point toward human-related rather than carnivore-related deposition. On the other hand, no direct micromorphological traces of intense human activity are recorded within the sediment, such as presence of charcoal, char, burnt bones, burnt sediments, or lithic chips (compare with Chagyrskaya Cave 3 ).
The upper boundary of layer F is erosional. It is covered by layer E, characterized by several features indicating its colluvial origin: i) unconformity at the bottom; ii) erosional channels locally at the bottom; iii) complex macroscopic texture with clasts of compacted sediments chaotically dispersed within loose matrix; iv) loose microscopic structure with packing voids ( Fig.S8: a, b); and v) presence of numerous clay balls, some of them containing bone fragments ( Fig.S8: a, b). A hiatus between layers F and E is possible filled by other layers of Series III (layers K2, L1 and L2), present in another part of the site. Layer K2, also analysed micromorphologically, exhibits similar features as the ones observed for layer E (Fig.S8: c, d).
Clay balls occurring within layers E and K2 resemble the material of layers F and G. This indicates that layers F and G were amongst the sources of material for colluvial activity, that deposited layer E and other layers of the Series III. This is an additional argument for linking the artefacts found within colluvial sediments of the Series III with artefacts and animal remains preserved in primary position within layer F.     III  5E  F  F  240-250  25 VI 68  50,39 29,71  12,61  14,67  65 flake  irregular  right angle triangular twisted  asymetric  yes  biderectional  yes  20  lateral right no  no  yes  right   alternated  platform  irregular  21,61 5,86  plan  no  no  plan  no  yes   472  1968  472  III  6E  F  F  250-260  25-26 VI 68 28,09 34,76  14,51  14,51  n flake  triangular  triangular  straight  asymetric  yes  unidirectional  no  no  no  yes  left  sharp  triangular  25,85 12,77  uncertain  yes  no  convex  no  yes  473  1968  473  III  5E  F  F  250-260  25-26 VI 68 45,91 36,28  10,15  10,15  65 flake  irregular  irregular  straight  asymetric  yes  biderectional  yes  10  lateral right no  big  no  central  sharp  irregular  23,  Bird assemblage analysis

Material and methods
Bird bones at Tunel Wielki Cave were excavated during the old (Chmielewski's) excavation as well as during the newest one. The former assemblage was already studied by Bocheński 1,2 and all the bones were ascribed to Holocene. This stratigraphy has been verified, and the bones rendered as Pleistocene's were reexamined. The bones from the newest excavations were identified by K. Wertz and Teresa Tomek; the bone surface was checked for possible human, animal, and environment modifications (see e.g. 3,4 ). For bone identification, the collection of ISEA PAS was used along with the bird bone identifications manuals 5 . In this study, only the bones attributed to Pleistocene layers are included. All bird bones from Tunel Wielki are stored at ISEA, PAS.

Results and comments
Bird bones from the Pleistocene layers at Tunel Wielki are very scarce (Table below). Domestic chicken (Gallus gallus): the bone (femur) was among the remains identified by Z.
Bocheński but it was not included in either of the papers (i.e. 1,2 ). The attached stratigraphic data, after revision, attribute the bone to the Pleistocene Layer J2, MIS 13-11. The reexamination of the bone confirmed it belongs to domestic chicken. The bone wears distinct traces of gnawing (very well preserved), its medullar cavity is filled with medullary bone, and the bone has creamy white color, similar to the bones in the Holocene's assemblage. Good state of the bone preservation, its taxonomic affiliation, and the fact that several chicken bones were found in the Holocene sediment, strongly suggest the bone is the Holocene's admixture.